1. Technical Field
The present invention relates to a delay circuit and an electronic device including a delay circuit.
2. Related Art
Currently, a delay circuit for delaying an input signal by a predetermined period is used for various purposes. Examples of unit for varying delay time of the delay circuit involve a digital variable delay circuit which varies delay by changing the row number of the circuit, and an analog variable delay circuit which varies delay by changing driving current or load given to a delay element. In case of the digital variable delay circuit, current consumption increases and accuracy lowers in proportion to the row number of the circuit.
In order to overcome this drawback, a method disclosed in JP-A-6-125252 changes power to be supplied to a delay circuit by switching a plurality of power sources using a switch to control delay time. According to the method shown in JP-A-6-125252, however, error is produced by ON-state resistance generated from the switch area. In this case, designing for producing desired delay is difficult.
As an improvement over this disadvantage, a method disclosed in JP-A-2006-217172 controls current and adjusts delay by using a current mirror so as to obtain delay in proportion to a control signal.
According to the method shown in JP-A-2006-217172, highly accurate control can be achieved. However, since delay is controlled by an analog method, control for obtaining desired delay is difficult.